I enjoy looking at photos from history, nature architecture etc. but what I might suggest to people posting them is to include some information about the photo. Especially if its a historical photo. Having context is huge. If you don't have any, perhaps share what makes the photo interesting to you or why you chose to share it. Obviously people will post what they will, I just find it far more appealing when there is more there. It's cool that we can post multiple images here with text, it allows a post to have more depth and even allows the user to create a narrative if they choose. Some creative uses of image posts: Hubski at the museum, Phone photography contest -prior to images in comments, and our fallen homie Major Khaaan Anyways, I think "historyporn" makes less sense than #historyphoto or even just #photography but then I realize there is a "history" to calling it that.
I'm inclined to start posting under #history given the context and not to create or use tags that aren't familiar and may fracture certain communities (read tags). Just my own personal preference given the community of users who are here and may end up coming here.